In 2014 voters approved a Washington initiative that requires buyers to undergo a background check when they purchase a gun from another private citizen.
Initiative 594 was designed to close the so-called "gun show loophole."
But analysis of federal data by the KING 5 Investigators raises questions about how effective that law has been.
Only 2% of background checks in Washington in 2015 stemmed from "private party" sales of guns, according to data in the FBI's National Instant Criminal Background Check – or NICS – system.
That number is surprising to researchers Philip Cook of Duke and Jens Ludwig of the University of Chicago, who study gun violence.
They say that their own research – and studies by others – have shown that up to 40% of gun sales nationwide are between private citizens. They're skeptical that the 2% reported to the FBI is an accurate picture of the private gun market in Washington state.
"I suspect…there are a lot of unreported private-market sales going on," Ludwig said in an email to KING 5.
In other words, the data could indicate that many gun sellers and buyers are evading the law.
"Jonathan" – who asked that we not reveal his real name – is one of them.
"People knew there was a threat to our rights," he said of I-594.
Jonathan says he's bought or sold several guns since the law went into effect.
"As far as following the law, roughly 50% of those (sales) I followed the law," Jonathan said.
Jonathan says many gun owners connect via private websites and meet up to buy and sell guns without the background check.
"If you hit me up on Facebook and say 'I'd like to buy your pistol', I can go through your Facebook right then and there and look at the kind of person you are right from your pictures," Jonathan said.
He says he uses his own means to determine if a buyer is a reasonable gun owner and doesn't believe that I-594 in constitutional.
Many others may be following suit.
NICS data shows that 170,876 background checks were conducted in Washington state between April and October of last year. The FBI started collecting the data from Washington in April.
Of all those background checks, only 3,290 of them – less than 2% -- were conducted for private party sales.
The data is entered by federally licensed firearms dealers. I-594 requires private buyers to report to a licensed dealer who conducts the background check – usually for a fee.
Firearms dealer Kelly Bachand, who owns Kelly's Gun Sales in Tukwila, say the low number may also be attributed to firearms dealers incorrectly filling out federal paperwork.
"It's not very obvious or easy to find the information as far as how it should be filled out," said Bachand.
It does not appear that anyone has ever been prosecuted for violating I-594. The Washington Administrative Office of the Courts says it does not have any record of anyone being charged under the law in 2015.
I-594 has stopped some felons from getting guns.
A firearms enthusiast in Snohomish County, who did not want to be identified, told KING 5 that he backed out of a deal when a background check identified the buyer as a felon.
Even so, the Snohomish County man feels I-594 is more of a hindrance on law-abiding citizens instead of criminals.
Even though he follows the law, he says there is much resentment in the gun community.
"I would say the majority of people who are buying and selling guns aren't following the law," the man said.